Apparatus for reproducing sound from sound records



W. C. BAILEY April 7, 1931.

APPARATUS FOR REPRODUCING SOUND FROM SOUND RECORDS Filed Dec.

l I m INVENTOR.

Patented Apr. 7, 1931 UNITED STATES ,PATENTOIFFICET WILLIAM CHARLES BAILEY, 0F COULSDON, ENGLAND, ASSIGNO R 0F ONE-Hull! TO JOHN IKEEFE, OF EASTNEY, ENGLAND APPARATUS non nnrnonuoms socnn FROM soulvn'nnconns Application filed December 21, 1929. Serial No. 415,771.

This invention relates to sound reproducing apparatus of the type in which a stylus is carried by a diaphragm, and engages the track of a sound record and in which the vibrations of the diaphragm are used to vary a magnetic field which controls an electric circuit in which is included a thermionic valve amplifying apparatus. The object of the present invention is to provide an improved sound reproducing apparatus which may be used either as an ordinary gramophone sound box or in combination with a thermionic valve amplifying apparatus whereby an additional volume of sound may be obtained which may be amplified to any required extent.

The present invention comprises a box or casing, a suitably held diaphragm carried therein and attached to a pivoted stylus arm carrying the needle, the said stylus arm having a triangular shape in cross section and adapted to form an armature, a permanent magnet carried by said box or casing and having its poles arranged adjacent to opposite sides of said armature and a pair of coils or bobbins, one on each of said poles and in circuit with a thermionic valve amplifying apparatus.

This invention will be now more particu larly described making reference to the accompanying drawing in which Fig. 1 is a view in front elevation of a sound box embodying the present invention.

Fig. 2 is a view in section on line 22 of Fig. 1.

Fig. 3 is a view in section on line 33 of Fi 1, and

Fig. i is a View in plan of a modification.

Throughout the views similar parts are marked with like letters of reference.

A box or casing apreferably of brass or other non-magnetic metalis provided with a diaphragm b to which a stylus arm 0 is fixed. The stylus arm 0 is pivoted to the box or casing at a and is formed at its lower end as a socket 0 to carry a needle :22. above described parts are of the usual well known construction, with the exception of the main portion of the stylus arm 0, which is of soft iron and of a triangular shape in cross So far, the

section adapted to form an armature of an electromagnet to be described. On the face of the box or casing a'is mounted a horse shoe magnet (Z, the poles d of which are arranged to come opposite to and nearly touch the opposite sides of the armature 0. The base or third side of the triangular shaped armature c is either adjacent to the diaphragm Z), as in Figs. 1-3, or remote therefrom as in Fig. l. On the pole pieces (Z are carried solenoids, coils or bobbins d in circuit with a thermionic valve amplifying apparatus of known construction.

The magnet (Z is either bent at its ends to bring the pole pieces d opposite the faces of the armature 0, as shown in Figs. 1-3, or is carried parallel with the face of the casing, as shown in Fig. 4 in which case the ends of the pole pieces (Z are bevelled to the same angle as the sides of the armature 0. Provision is preferably made for adjusting the position of the pole pieces (l1 with respect to the armature. A convenient arrangement is that shown wherein the magnet 01 is carried on the casing a by means of bolts 6 and interposed washers 6 which are preferably resilient, for instance of india rubber. By such an arrangement, it will be seen that by adjusting the nuts of the bolts 6 the magnet d may be caused to approach or recede from the casing a thereby adjusting the pole pieces 65 in relation to the armature 0.

I declare that what I claim and desire to secure by Letters Patent is 1. Apparatus for reproducing sound from sound records, comprising a casing, a diaphragm held therein, a stylus bar attached to said diaphragm and pivoted to the casing, said stylus bar having a triangular shape in cross section and forming an armature for an electromagnet, a permanent magnet carried by the casing, and having its poles arranged in close proximity to the opposite sides of the armature, and a pair of coils or bobbins, one on each of said poles and in circuit with a thermionic valve amplifying apparatus, as set forth.

2. Apparatus for reproducing sound from sound records, comprising a casing, a diaphragm held therein, a stylus bar attached to said diaphragm and pivoted to the casing, said stylus bar having a triangular shape in cross section and forming an armature for an electromagnet, a permanent magnet carried by the casing and having its poles arranged in close proximity to the opposite sides of the armature, a pairof coils or bobbins one on each of said poles and in circuit with a thermionic valve amplifying apparatus, and means for adjusting the pole pieces of the magnet in relation to the direction of movemen of the armature, as set forth.

WILLIAM CHARLES BAILEY. 

